Robust position tracking control of a camless engine valve actuator with time-varying reference frequency

This paper presents robust position tracking control of an electro-hydraulic camless engine valve actuator with the reference of time-varying frequency. The valve actuator includes nonlinearities associated with the hydraulic flow and the nonlinear friction. To retain such nonlinearities, the stabilized valve actuator is modeled as a block-structured system using the Volterra series representation. For tracking control design, the extended generating dynamics, which is justified by frequency domain analysis of a feedback system, is applied to the robust time-varying tracking control which is based on the internal model principle. The given tracking control method is illustrated by both simulation and experiments. With the extended generating dynamics, tracking the reference of time-varying frequency shows significant improvement.